Physics: The physics of swings

This week we continued our investigations into playground physics. The kids set out to understand what a swing is by building them out of Kinex. Once we had a few models to compare, we were able to consider what sorts of changes we could make to the design to affect the swing's period, the time it takes to swing back and forth. The kids came up with a few different variables: the mass of the swing, the length of the swing, and the height or angle at which you start the swing. Like our experiments with friction, we plan to test these variables in the field, on actual swings. Next week (weather-permitting) we'll visit a playground and see which of these variables affects a swing's period the most.

General Science: Indicators for acids and bases

This week we learned about acids and bases and two types of indicators you can use to identify them. We began by using red and blue litmus paper to test different household liquids. We were then able to classify them as acids, bases, or neutral. However while litmus paper is useful, it doesn't tell you anything about how strong or weak a base or acid is. So, for example, while baking soda and bleach, the two bases we encountered, score the same on a litmus test, baking soda tastes mildly bitter whereas tasting bleach will land you in the hospital (hypothetically speaking, of course!). We observed that in order to appreciate this without landing in the hospital, pH paper comes in real handy.

General Science: Dry Ice

We started off the session by discussing what makes dry ice so COOL.

While it looks like regular water ice, it is actually frozen carbon dioxide. It is genuinely cooler than regular ice. That's why we ONLY handled the dry ice with tweezers. Possibly the coolest part is how it sublimes, meaning it changes directly from solid into a gas, skipping the liquid phase.

Then we demonstrated its coolness in the following ways....

• froze cooked pasta and flowers by dropping them in acetone with dry ice. (Acetone is good thermal conductor, so it gets really really cold.)

• produced a lot of spooky fog.

• "poured" carbon dioxide gas into a cup on a scale and noted that it weighed more than an equal volume of air.

• used carbon dioxide gas as a fire extinguisher (Don't panic, the fire was a single lit candle).

• measured temperature changes in water after adding dry ice.

• made the dry ice "squeal" and vibrate after pressing it with a metal spoon.

• inflated a latex glove by putting a piece of dry ice inside and then tying off the open end.

• produced a loud popping sound by placing a piece of dry ice in a small plastic container and then closing it.

Physics: Dry Ice

We started off the session by discussing what makes dry ice so COOL.

While it looks like regular water ice, it is actually frozen carbon dioxide. It is genuinely cooler than regular ice. That's why we ONLY handled the dry ice with tweezers. Possibly the coolest part is how it sublimes, meaning it changes directly from solid into a gas, skipping the liquid phase.

Then we demonstrated its coolness in the following ways....

• froze cooked pasta and flowers by dropping them in acetone with dry ice. (Acetone is good thermal conductor, so it gets really really cold.)

• produced a lot of spooky fog.

• "poured" carbon dioxide gas into a cup on a scale and noted that it weighed more than an equal volume of air.

• used carbon dioxide gas as a fire extinguisher (Don't panic, the fire was a single lit candle).

• measured temperature changes in water after adding dry ice.

• made the dry ice "squeal" and vibrate after pressing it with a metal spoon.

• inflated a latex glove by putting a piece of dry ice inside and then tying off the open end.

• produced a loud popping sound by placing a piece of dry ice in a small plastic container and then closing it.